This invention relates to generation of speech. More particularly, this invention relates to a computer-based system that can be used by a person having aphasia, or another condition which impairs normal human speech functions, in order to assemble and deliver a speech message.
Aphasia is a language disorder caused by stroke or other injury to the brain; some form of aphasia afflicts over two million Americans. Aphasia interferes with the ability to select words and assemble the selected words in accordance with syntax rules to form sentences communicating an intended meaning. Computer technology has been employed to assist in the mechanics of communicating with aphasic patients. For instance U.S. Pat. No. 5,169,342 to Steele et al. describes a graphically based communication system that is provided to the user with a stored set of words and associated icons that have been selected by the system provider as the universe of words available for use during a communication session. The icons are selected to visually represent the meaning of the words with which they are associated, for instance an image of a cigarette with a diagonal line through it to represent the word "nonsmoking". The system includes a phrase window where icons are displayed in an ordered manner to represent a sentence composed of the words they represent, and an access window where icons representing candidate words for possible inclusion in a sentence may be displayed. The system displays in the phrase window the icons representing a sentence which is selected, by means which are not apparent, as appropriate for the communication session. An aphasic patient uses the system to communicate by manipulating a mouse to replace icons in the displayed phrase with other icons representing the words the patient intends to communicate. The candidate replacement words for a displayed word are selected by the system as being paradigmatic alternatives for the displayed word in the sentence syntax. Thus the use of the system entails an iterative process including the comprehension of the syntax of the sentence represented by the displayed icons, identification of a sentence component that is at variance with the user's intended meaning and therefore is to be replaced, exploration of the set of paradigmatic alternatives provided by the system for the word to be replaced, selection of a replacement word, and repetition of these steps until the user is satisfied with the sentence as representing an intended meaning. This system has a number of drawbacks. By relying on a set of stored words, a tradeoff is created between search time and accuracy of meaning; a small vocabulary is more quickly searched but may lack words to convey a particular meaning, and a vocabulary large enough for communication of a wide range of meanings may require so much time to search for the right word as to be impractical for communication. This is particularly problematic since aphasics generally have difficulty with the linguistic and mechanical steps involved in constructing a sentence using the system. Moreover, at each step of the process the user must glean the meaning of a word from its icon. Icons are frequently enigmatic, and it may be quite difficult to ascertain the meaning of a vocabulary word from its icon and time-consuming to access further data that explains the meaning of an icon. This is particularly problematic with functional words, which are difficult to represent by an informing icon but which are often critical to the meaning of a sentence. The prior art systems for assisting aphasics in sentence construction are cumbersome, slow, and difficult to use.